In EMG, the electrical activity of muscle tissue is recorded and interpreted. When a muscle fibre contracts, a potential is generated. Signals from a given muscle, or group of muscles, can be detected by use of an appropriately situated electrode. This is generally achieved by use of a needle probe having a conducting inner core fixed within a conducting outer cannula, the two being insulated from each other by an intervening insulating layer. The conductive parts of the needle are connected to separate pins of a plug for attachment to the recording equipment. Conventionally, this is achieved by use of separate connecting pins attached to the outer cannula and attached to the inner core, which generally consists of a metal wire.
During an EMG procedure, it is often necessary to use such a probe to take a number of measurements for a single patient. However, to reduce risk of infection to patients, it is desirable to dispose of a needle altogether after it has been used for one patient. This is an expensive procedure if conventional needle probes are used, as several manufacturing stages are required to produce the needle probe, which comprises not only a needle but also an electrical plug. It is thus desirable to provide a new design of needle probe in which new needles can be used for each patient without there being a need to replace an expensive part each time that this is done.
A potential line of development is to simplify the disposable part. This however poses difficulty, because of the need to provide reliable electrical connection between the plug of the probe and, separately, the inner core and the outer cannula.